A plastic tank must be operated at
atmospheric pressure (air must enter and exit the tank as it is filled and emptied).
All of our above-ground tanks come with a vented manway. If 3” or 4” outlets are
used or rapid dispensing is possible, an additional vent fitting should be considered.
Check chemical compatibility chart
for appropriate fitting and gasket material.
- The fitting must be above the
bottom knuckle radius of the tank (the curve which is formed inside the tank, blending
the side wall with the bottom). On rectangular tanks, the fitting must not be installed
too close to the adjacent wall. Good gasket compression is necessary for a leak-proof
See chart for maximum fitting size.
- To drain a tank below the outlet
fitting location, you may use a siphon drain
- Mark the position of center point
of the fitting on the outside of the tank with a grease pencil or marker.
- Cut a hole in the tank using
a hole saw of the proper diameter. The proper diameter is found by measuring the
outside thread diameter of the fitting body. It is advisable to cut a hole
in a scrap of plastic or wood and test fit the bulkhead through the hole. It should
pass into the hole but should not have more than a maximum of 1/16th inch of side-to-side
Hint: If access to the inside of tank is limited (manway too small
to reach into the tank or the tank is too big to move easily around), use a string
as a guide for the bulkhead fitting. Cut a length of string 3 times the distance
from the tank manway to the fitting hole. Run the string from manway through the
fitting hole. You may have to fish the string through the fitting hole by using
a stick to pull the string through the hole (duct tape on the end of the stick
will help the process). Put the gasket on the fitting body and pass the string through
the body. The gasket side of body should be facing the fitting hole. Tie a pencil
or stick behind the fitting. Pull string from fitting hole to lead the fitting.
When fitting is through the hole, attach nut and release the string.
- The nut must now be tightened
(hand tightened only). If you have installed a siphon tube, be certain that is facing
the correct direction.
- The tank will expand and contract.
Flexible connections must be used between tank fitting and rigid pipe or pump.
- Water test your tank to check